In the Laboratory
Teflon Tape—The Leaky Buret Remedy Brett C. Boshco and John J. Griffin* Westwood High School, 2000 Nahatan St., Westwood, MA 02090; *
[email protected] Burets used by high school and college students for classical titrations may be purchased with three separate interconnecting components consisting of the main glass stem, a stopcock (usually made primarily out of Teflon), and a replaceable glass capillary tip. The replaceable glass tip makes the three-component buret more attractive than the unibodyconstructed buret, which may become permanently inoperable if the capillary tip becomes clogged with grease, dirt, or soap powder. Ironically, replacement of these tips may prove to be quite challenging owing to variations in the external diameter of the replacement glass tips. These diameter variations are frequently the cause of leaks and they prevent the buret
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from being used effectively. In many cases, the application of silicone grease proved to be inadequate in correcting leaks. As a remedy for buret leaks caused by an improper tip-to-stopcock fit, Teflon tape (1.2 cm in width), available in most hardware stores, should be wrapped tightly around the glass tip before it is inserted into the buret’s stopcock. When inserting the glass tip into the stopcock, rotate the glass tip in the direction opposite to the direction in which the tape is wrapped around the glass. The Teflon tape will fill voids as the glass tip is pushed up into the stopcock, providing the seal needed where silicone grease failed.
Journal of Chemical Education • Vol. 77 No. 10 October 2000 • JChemEd.chem.wisc.edu
